1. Field of the Invention
The present invention relates to a method for applying a failure detection protocol to an aggregated link using a communication protocol in the transport layer.
2. Description of the Related Art
The official standard for link aggregation is described in IEEE802.3ad. According to the technology described in IEEE802.3ad, the capacities of multiple physical links can be combined into one logical link to increase the bandwidth. The aggregated link is made to appear to the layers equal to or higher than the network layer of the OSI reference model, such as IPv4 or IPv6, as one MAC.
The standardization work of BFD (Bidirectional Forwarding Detection) is carried out by IETF (Internet Engineering Task Force) for creating a routing-protocol-independent protocol for detecting a communication failure between next-hops (see Bidirectional Forwarding Detection, draft-ietf-bfd-base-5, June, 2006 and BFD for IPv4 and IPv6 (single hop), draft-ietf-bfd-v4v6-1hop-5 June, 2006). BFD uses UDP to send and receive packet regularly between systems and, if packets are not received for a predetermined time, determines that a communication line failure has occurred. Usually, BDF performs the failure monitoring of a communication line based on a request from a routing protocol. When a failure monitoring request is generated for the same data protocol path from multiple routing protocols, BDF performs the monitoring in a single BFD session.